For the past 15 years, zero-tolerance policies for violence in schools have been the driving force behind many--80 to 95 percent by some estimates--of school discipline policies around the country. Starting in 1994 with the requirements of the federal Gun-free Schools Act and propelled by the shootings at Columbine High School five years later, districts began implementing zero-tolerance polices not just on possessing weapons but on a variety of student behaviors--from bringing in drugs and alcohol to cursing, disrupting class or even violating the dress code. Along the way, student suspensions and expulsions multiplied, not to mention the number of referrals to principals' offices across the nation. (Excerpt).